Paper manufacture



Patented Apr. 20, 1937 UNITED STATES PAPER, MANUFACTURE Harold Robert Rafton, Andover, Mass., assignor to Rafiold Process Corporation, a corporation of Massachusetts No Drawing. Application April 14, 1932, Serial No. 605,347

34 Claims.

aration of a dry mixture of alkaline filler, acidic material and size.

A further object of the invention is the employment of these dry mixtures in the manufacture of paper filled with alkaline filler, under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix. 0

Other objects and advantages of the invention will become apparent during the course of the following description.

In a number of my patents and copending ap- 5 plications relating to paper filled with alkaline filler, I have disclosed methods for the addition of the various ingredients, either to the paper mix under conditions favoring the minimizing of time and/or intimacy of contact of the-constituents of the mix, or directly,to the paper web.

According to those disclosures, ingredients such as alkaline filler, size, sodium silicate, acidic material such as alum, starch and the like, may be added late in the papermaking process'that is to say subsequent to the beater, as for example at the dilute stage, or to the forming or already formed web. These ingredients I have found may conveniently be added individually in dry form, although where alkaline filler is one of the :0 ingredients and none of the others added is chemically incompatible therewith, they may if desired be added together in the wet condition.

I have found-that it is sometimes advantageous to add together ingredients which for example include alkaline filler, even when they are chemically incompatible. If the effects of the individual incompatible ingredients are to be obtained in the fibrous mix, this joint addition is obviously not feasible when the ingredients are in 5 the wet condition unless the mixture of the alkaline filler and the chemically incompatible ingredient or ingredients is made just prior to their addition to the fibrous mix.

However, I have found that if the desired materials be mixed in the dry form this difficulty is obviated, and two or more of the chemically incompatible ingredients such for example as alkaline filler, size,-alum, or the like, can thus be added together with distinct advantage in certain cases.

While such dry mixtures may be added at any stage of the papermaking process, it is particularly advantageous to add them under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the fibrous mix. As has been explained in great detail in a number of my patents referred to above (see for example United States Patents Nos. 1,803,642, 1,803,643, and 1,803,645-1,803,652. inclusive, all issued May 5, 1931), such conditions exist in paper manufacture, from the standpoint of favoring the minimizing of the time of contact, when the mix is to remain in the concentrated condition only for a relatively short period of time, which period may for example be very brief such as at any time between the passage of the fibrous mix from the machine chest and its delivery to the web-forming device; and from the standpoint of favoring the minimizing of intimacy of contact, for example at any point between that of dilution of the fibrous mix at the mixing box or other eguivalent device and the point of its delivery to the web-forming device of the paper machine. By machine chest is meant the last stock-containing chest prior to the paper machine.

It will be apparent that the fibrous mix up to the point of dilution is in the relatively concentrated condition, whereas from the point of di-' lution to the point of delivery to the web-forming device, it is in relatively dilute condition. I have found that the introduction of the dry mixture into the fibrous mix while the fibrous mix is inv the relatively concentrated stage; for example as it is being mixed in preparation for leaving or just after it leaves the machine chest, is at times advantageous in certain cases, e g. in very hard sized papers. In other cases, however, e. g. in moderately sized papers and substantially unsized papers, I have found that at times it is advantageous to add the dry mixture at the dilute stage. Thus, in the practice of my invention I may add the dry mixture under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the fibrous mix.

Or I may at times even add it to the forming web at any point prior to the passage of the web from the web-forming device, but in most cases I prefer to add the dry mixture to the fibrous mix at the dilute stage of the papermaking process.

An example of a dry mixture which may be used in the practice of my invention is alkaline filler and alum. These two ingredients may be mixed dry, and ground if desired, and the mixture employed in the papermaking operation. The alkaline filler used is preferably already in a fine state of subdivision and the alum is preferably finely comminuted. Likewise, dry alkaline filler may be mixed with dry size, such as rosin size, together with a dry precipitant for the same such as alum, and used in my process. Likewise, also, dry alkaline filler and dry size, although not chemically incompatible, may with advantage be mixed, and then added in the papermaking operation. Dry alkaline filler may also be used with dry starch, dry sodium silicate, and the like, with or without dry acidic material such as alum. In certain cases also dry fibrous material may be incorporated in one or more of the mixtures described, but such resulting mix- .tures are in most cases more adaptable for addition to the fibrous mix when it is in the concentrated condition rather than in the dilute, because of the lack of time in many cases for thoroughly wetting up such fibrous constituents at the dilute stage.

Examples of specific dry mixtures which I may use in the practice of my invention follow:

(1) A mixture of alkaline filler containing 8 per cent. by weight of acidic material, such as alum, may suitably be used in the manufacture of papers in which approximately 25 per cent. of the total furnish is alkaline filler, and where normally 2. per cent. alum on the weight of the furnish is satisfactory. This may be used in the manufacture of either sized or unsized papers.

(2) A mixture of alkaline filler and size, for use in the manufacture of sized paper where the alkaline filler is used for example to the extent of approximately 20 per cent. on the total furnish, would be one in which size in an amount of approximately 10 per cent. on the weight of the alkaline filler would be employed.

(3) A mixture of alkaline filler, size and acidic material such as alum, for use in sized papers where the alkaline filler is used for example to the extent of 20 per cent. on the total furnish, would be one in which size andalkaline filler may be used in the same proportion as given in Example (2), and alum may be used in an amount of approximately 1 to' 2 times the weigth of the size.

While the above are examples of dry mixtures which may be used in practicing my invention, of course I do not limit myself thereto, as it will be apparent for example that other proportions,

both of the several ingredients to one another and to the entire furnish may be used according to conditions. In general, however, it may be stated that where it is desired that the quantities of the ingredients added as a dry mixturev shall be substantially the only quantities of said ingredients added to a mix, the proportions of the several ingredients to one another in the dry mixture, as well as to the total weight of the furnish, will in any given instance be substantially the same as if the ingredients were added independently. Where other quantities of one or more of the ingredients are added in the papermaking process apart from these quantities added in the dry mixture, then the quantities of ingredients in the dry mixture and the total amount of the dry mixture added, should be regulated accordingly, as will be apparent to the skilled papermaker.

In the preferredv practice of my invention, I mix in a beater or other suitable apparatus the fibrous material, and such other ingredients as I do not desire to supply later in dry admixture for example, subject the fibrous mix to the usual mechanical treatment, and at the point where the fibrous mix is diluted preparatory to delivery to a Web-forming device, I add a desired dry mixture such as described above. The web is then formed, dried as usual, and finished as by calendering if desired. Papers of excellent quality filled with alkaline filler are thus produced, either sized or unsized as desired.

One advantage of using such dry mixtures as I describe lies in the feasibility of properly proportioning the various ingredients prior to their use in papermaking. They may if desired be shipped in this condition. However, where the vides a very convenient means of handling the' various ingredients and at times makes for considerable economy in their use. owing to the ease of control, and the avoidance of the waste which sometimes accompanies the handling of liquids. Another advantage is that the prior mixing to which the ingredients are subjected assists the intimate mixture desired to be obtained between the various constituentsin the fibrous mix, and thus in certain cases makes for substantially improved results.

I am aware that it has been previously proposed to mix alum and calcium carbonate dry and use the mixture as a water coagulant, the calcium carbonate being present in such an amount as will, together with the alkaline content of the Water, completely react with the alum. It is apparent that in such coagulant the alum is present in some degree of stoichiometrical excess over the calcium carbonate, except in such limiting condition where the water to be treated contains no alkaline content, in which case the alum and'calcium carbonate would be present in the coagulant in substantially chemically equivalent proportions. I am also aware that it has been previously proposed to mix dry calcium carbonate and alum in substantially chemically equivalent proportions and to use such'material in paper manufacture for addition to the furnish or to the white paper, for purposes of coagulation. It will be apparent, however, that in the case where alkaline filler and alum are to be jointly used the present invention does not contemplate chemically equivalent proportions of alkaline filler such as calcium carbonate, and alum, but rather contemplates that the alkaline filler'is to be present in substantial stoichiometrical excess over the alum. For instance, 1 part of calcium carbonate is chemicallyequivalent to 2.2 parts of commercial alum. Thus, in Example (3) above the calcium carbonate is present in an amount 11 to 14.7 times, and in Example (1) in an amount 27.5 times, the chemical equivalent of the alum.

acidic material, instead of alum, with a certain measure of success I may usealone or in combination other acidic materials, such as other compounds of aluminum, or acids existing in the solid state such as oxalic or tartaric, or metallic salts such as sodium bisulphate or compounds of zinc, tin or the like.

For size that is to say sizing ingredient I prefer rosin size, which is meant to include any sizing agent which comprises ro sin and/or compound and/or derivative thereof, but instead of. rosin size I may use any size which may be used in the paper industry, for example saponified fatty acids or the like, or emulsions of various materials such as parailin, or any other size which may be reduced to substantial dryness (and be capable of being wetted with water when dry) and which may for example be mixed with alkaline filler dry, or which may be admixed wet with alkaline filler and subsequently dried, in any case, however, the resultant dry mixture should be such as to be capable of being wetted with water. apparent, however, that by the word size, sizing or the words sizing ingredient as used herein I mean material which is intended eventually to impart water resistance in some degree to the paper, and do not mean material such as starch or glue.

By the term alkaline filler I mean substantially water insoluble filler which when agitated in contact with freshly boiled distilled water, say for an hour, will impart a pH value to such water greater than 7.0, that is, which will be on the alkaline side of the neutral point. Among fillers included in this group may be mentioned calcium carbonate, of which'lime mud from the causticizing process is one form; calcium carbonate magnesium basic carbonate employedinthe paper disclosed in my United States Patent No. 1,595,416 of August 10, 1926; calcium carbonate magnesium hydroxide disclosed in my United States Patent No. 1,415,391 of May 9, 1922; and other substantially water insoluble normal or basic carbonates of alkaline earth metals, (which expression is herein intended to include magnesium), or compounds, double salts, or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature.

When I use the word paper" herein, I use it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Fourdrinier, cylinder, or other forming, felting, shaping or molding machine.

I speak herein of dry" mixtures or ingredients. By dry" I mean to include not only the case where such material is bone dry, i. e. 100 per cent. dry, but also the case where it appears to be substantially dry to sight and touch but where however a certain amount of moisture may be present. The presence of such an amount of moisture in certain of the dry ingredients is sometimes of specific advantage in that it allows the material to be more readily wetted by water, and also at timesprevents a colloidal condition in an original wet material from being converted into an irreversible gel condition, which would take place if the material were bone dried instead of being dried to apparent dryness but still containing a certain residual moisture content. One example of this is certain types of dry alkaline filler; another is certain types of dry size.

While I have described in detail the preferred embodiments of my invention, it is to be understood that the details of procedure, the proportions of ingredients, and.- the arrangement of steps may be widely varied without departing from the It will be a spirit of my invention or the scope of the sub joined claims.

I claim:

1. The step in a method of manufacturing paper filled with alkaline filler comprising adding in the paper-making process prior to the passage ,of the web from the web-forming 'device a dry mixture of alkaline filler and at least one member of a group of papermaking ingredients which in clude size and acidic material, the alkaline filler being present-substantiallyin excess in respect (tic the chemical equivalent of any acidic ingreient.

2. The step in a method of manufacturing paper filled with alkaline filler comprising adding in the papermaking process under conditions favoring the minimizing of the time of contact of the constituents of the mix a dry mixture of alkaline filler and at least one member ofv a group of papermaking ingredients which includes size and acidic material, the alkaline filler being present substantially in excess in respect to the chemical equivalent of any acidic ingredient.

3. The step in a method of manufacturing paper filled with alkaline filler comprising adding in the papermaking process under conditions favoring the minimizing of the time and intimacy of contact of the constituents of the mix a dry.

mixture of alkaline filler and at least one member of a group of papermaking ingredients which includes size and acidic material, the alkaline filler being present substantially in excess in respect to the chemical equivalent of any acidic ingredient.

4. The step in a method of manufacturing paper filled with alkaline filler comprising adding at the dilute stage of the papermaking process a dry mixture of alkaline filler and at least one member of .a group of papermaking ingredients which includes size and acidic material, the'alkaline filler being present substantially in excess in respect to the chemical equivalent of any acidic ingredient.

5. The step in a method of manufacturing paper filled with alkaline filler comprising adding in the papermaking process prior to the passage of the web from the web-forming device a dry mixture composed of alkaline filler and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

6. The step 'in a method of manufacturing paper filled with alkaline filler comprising adding in the papermaking process under conditions favoring the minimizing of the time of contact of the constituents of the mix a dry mixture composed of alkaline filler and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

7'. The step in a method of manufacturing paper filled with alkaline filler comprising adding in the papermaking process under conditions favoring the minimizing of the time and intimacy of contact of the constituents of the mix a dry mixture composed of alkaline filler and acidic material, in which the alkaline filler is present substantially'in excess of the chemical equivalent of the acidic material. I

8. The step in a method of manufacturing paper filled with alkaline filler comprising adding at the-dilute stage of the papermaking process a dry mixture composed of alkaline filler and acidic material, in. which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

9. In a method of manufacturing paper filled with alkaline filler wherein acidic material is employed, that step comprising adding a dry mixture of alkaline filler and size in the papermaking process prior to the passage of the web from the web-forming device.

10. In a method of manufacturing paper filled with alkaline filler wherein acidic material is employed, that step comprising adding a dry mixture of alkaline filler and size in the papermaking process under conditions favoring the minimizing of the time of contact of the constituents of the mix.

11. In a method of manufacturing paper filled with alkaline filler wherein acidic material is employed, that step comprising adding a dry mixture of alkaline filler and size in the papermaking process under conditions favoring the minimizing of the time and intimacy of contact -of the constituents of the mix.

12. In a method of manufacturing paper filled with alkaline filler wherein acidic material is employed, that step comprising adding a dry mixture of alkaline filler and size at the dilute stage of the papermaking process.

13. The step in a method of manufacturing paper filled with alkaline filler comprising adding in the papermaking process prior to the passage of the web from the web-forming device a dry mixture of alkaline filler, size and acidic material, the alkaline filler being present substantially in excess'of the chemical equivalent of the acidic material.

14. The step in a method of manufacturing paper filled with alkaline filler comprising adding in the papermaking process under conditions favoring the minimizing of the time of contact of the constituents of the mix a dry mixture of alkaline filler, size and acidic material, the alkaline filler being present substantially in excess of the chemical equivalent of the acidic material.

15. The step in a method of manufacturing paper filled with alkaline filler comprising adding in the papermaking process under conditions favoring the minimizing of the time and intimacy of contact of the constituents of the mix a dry mixture of alkaline filler, size and acidic material, the alkaline filler being present substantially in excess of the chemical equivalent of the acidic material. a

16. The step in a method of manufacturing paper filled with alkaline filler comprising adding at the dilute stage of thepapermaking process a dry mixture of alkaline filler, size and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

1'7. A raw material for the paper industry comprising a dry mixture of alkaline filler and at least one member of a group of papermaking ingredients which includes size and acidic mate- Y rial, the alkaline filler being present substantially in excess in respect to the chemical equivalent of any acidic ingredient. 18. A raw material for the paper industry: a dry mixture composed of alkaline filler and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

19. A raw material for the paper industry: a. dry mixture composed of alkaline filler, comprising calcium carbonate, and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

20. A raw material for the paper industry comprising a dry mixture of alkaline filler, comprising calcium carbonate and magnesium compound, and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

21. A raw material for the paper industry comprising a dry mixture of alkaline filler, comprising calcium carbonate magnesium hydroxide, and acidic material, in which the alkaline filler is present substantially in excess of.the chemical equivalent of the acidic material.

22. A raw material for the paper industry: a dry mixture composed of alkaline filler and metallic salt, in which the alkaline filler is present substantially in excess of the chemical equivalent of the metallic salt.

23. A raw material for the paper industry: a dry mixture composed of alkaline filler and substantially water solublecompound of aluminum, in which the alkaline filler is present substantially in excess of the chemical equivalent of the compound of aluminum.

24. A raw material for the paper industry: a dry mixture composed of alkaline filler and alum, in which the alkaline filler is present substantially in excess of the chemical equivalent of the alum.

25. A raw material for the paper industry comprising a dry mixture of alkaline filler and rosin size.

26. A raw material for the paper industry comprising a dry mixture of alkaline filler, size and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

27. A raw material for the paper industry comprising a dry mixture of alkaline filler, size and alum, in which the alkaline filler is present substantially in excess of the chemical equivaa lent of the alum.

28. In a method of manufacturing paper filled with alkaline filler wherein size is employed, that step comprising adding in the papermaking process prior to the passage of the web from the web-forming device a dry mixture of alkaline filler and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

29. In a method of manufacturing paper filled with alkaline filler wherein size is employed, that step comprising adding in the papermaking process under conditions favoring the minimizing of the time of contact of the constituents of the mix a dry mixture of alkaline filler and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

30. In a method of manufacturing paper filled with alkaline filler wherein size is employed, that step comprising adding in the papermaking process under conditions favoring the minimizing of the time and intimacy of contact of the constituents of the mix a dry mixture of alkaline filler and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

31. Ina method of manufacturing paper filled with alkaline filler wherein size is employed, that step comprising adding at the dilute stage of the papermaking process a dry mixture of alkaline filler and acidic material, in which the alkaline filler is present substantially in excess of the chemical equivalent of the acidic material.

32. In a method of manufacturing paper filled with alkaline filler wherein the ingredients employed comprise fibrous material, alkaline filler,

sizing ingredient, and acidic material, that step comprising adding to the fibrous mix under conditions favoring the minimizing of the time of contact of the constituents of the mix, a dry ingredient in admixture with another airy ingredient to react with each other after addition to said fibrous mix.

33. In a method of manufacturing paper filled with alkaline filler wherein the ingredients employed comprise fibrous material, alkaline filler, sizing ingredient, and acidic material, that step comprising adding to the fibrous mix, under conditions favoring the minimizing of the time of contact of the constituents of the mix, dry sizing ingredient in admixture with dry acidic material to react with each other after addition to said fibrous mix.

34. In a method of manufacturing paper filled with alkaline filler wherein the ingredients employed comprise fibrous material, alkaline filler, sizing ingredient, and acidic material, that step comprising adding to the fibrous mix, under conditions favoring the minimizing of the time of contact of the constituents of the mix, dry size and dry alum in admixture to react with each other after addition to said fibrous mix.

HAROLD ROBERT RAFTON. 

